According to the CDC, 159 measles cases -- the second-largest number since U.S.-originated cases were eliminated in 2000 -- had been reported across the United States as of Aug. 24, more than a month before the beginning of the fourth quarter of 2013. Sixteen states have reported measles cases, with ages of the infected ranging from birth to 61 years. No deaths have been reported.

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According to the CDC, 159 measles cases had been reported as of Aug. 24 -- the second largest number since U.S.-originated cases of the viral infection were eliminated in the United States in 2000.

One hundred thirty-one cases were in unvaccinated individuals, 79 percent of whom had philosophical objections to the vaccine.

In all of the cases, the virus was imported into the country from abroad.

In all of the cases, the virus was imported into the country from abroad.

"Importation of measles (into the United States) continues to occur, and it poses … a particular threat to people who are not vaccinated," Schuchat said. "There were 42 actual importations from 18 other countries. Half of the imported measles cases …originated from Europe, not a place that many people think of when they try to update their vaccine records before travel."

"These diseases are still out there," she said. "They are literally a plane ride away, and every day, about 11,000 babies are born in the United States completely vulnerable to all of these diseases."

It's worth noting, said Schuchat, that the VFC program originally was created to combat a significant resurgence of measles in the United States from 1989 to 1991.

"About 55,000 cases of measles were reported in the United States, and 123 people died," she said. "Hardest hit were unvaccinated preschool-age children, many from low-income, inner-city families. The measles virus finds unimmunized people."

Although the current spate of measles infections is a far cry from the crisis that occurred more than two decades ago, said Schuchat, physicians and other health professionals need to stay ahead of the virus by making sure that immunization coverage is as complete as possible.

"Thirty-seven percent of the (currently reported) cases were children under 5, and 13 percent of all cases were in babies under 12 months, who are too young to be routinely vaccinated," she said.

Most of this year's cases -- 131 -- were in individuals who had not been vaccinated, with New York, Texas and North Carolina leading the case report numbers. Seventy-nine percent of unvaccinated individuals had religious or philosophical objections to the vaccine.

"As these outbreaks are showing, clusters of people with like-minded beliefs leading them to forgo vaccines can be susceptible to outbreaks when measles outbreaks are imported from elsewhere," Schuchat said. "Measles, as we know, is highly contagious and can lead to serious complications and even death. We need very high rates of immunization to protect the most vulnerable: children too young to be vaccinated and those who can't be vaccinated due to health conditions."

Schuchat reiterated the importance of conversations between physicians and patients about vaccination coverage.

"A clinician's strong recommendation is very important," she said. "It's also important for clinicians to listen and to make sure they understand what concerns and questions the parents have and that they address them and take them seriously. Because, bottom line, the parents want to keep their children healthy and they want good information in order to do that."